Alkalinity

Alkalinity is the acid-neutralizing capacity of seawater, defined as the excess of proton acceptors over proton donors relative to a zero level of protons. Total alkalinity is dominated by bicarbonate and carbonate ions, with smaller contributions from borate, hydroxide, and minor bases. Surface ocean total alkalinity runs near 2,300 micromoles per kg and tracks salinity closely. With dissolved inorganic carbon, alkalinity is one of the two master variables that fix the entire carbonate system, so paired measurements let you compute pH, pCO2, and the carbonate-ion concentration that controls calcite and aragonite saturation.